Welcome back to our HVAC blog series! This time, we’re taking a look at possible problems with gauge pressure and compression.
If you’re having another issue, please take a look at Ambulance HVAC Troubleshooting: Common Issues with Simple Fixes or our other blog posts that cover other prevalent HVAC issues.
When looking for possible issues with gauge pressure and compression, please pay close attention to the compressor suction and discharge pressures. At a range of 30 – 38 degrees Celsius (86 – 96 degrees Fahrenheit), the blower speed set to HI (high speed), the temperature switch set to full cooling, and an engine speed of roughly 1,500 RPM, you should look for the following numbers to stay within normal ranges:
- High-Pressure Side Pressure: 1.5 – 1.7 Mpa (15 – 17 kg/cm, 213 – 242 psi)
- Low-Pressure Side Pressure: 0.13 – 0.2 Mpa (1.3 – 2.0 kg/cm, 18 – 28 psi)
If your unit is falling outside of those ranges, there are a number of possible issues depending on the specific range of the issue. Please refer to the following sections for additional steps on troubleshooting these issues.
Low-Pressure Side Pressure is Too High:
- Defective Thermo-Switch: If the magnetic clutch switch is turning off before the outlet air temperature is low enough, the switch may be faulty, and should be replaced.
- Defective Compressor Gasket: If the high-pressure and low-pressure side pressures equalize when the magnetic clutch is turned off, you may be having an issue with the compressor. Replacing it should resolve the issue.
- Poor Expansion Valve Temperature Sensor Contact: Look for signs of frost stuck to either the suction hose or the pipe. If frost is detected, you can combat this by installing the temperature sensor against the low-pressure pipe.
- Expansion Valve is Open too Far: Once again, look for signs of frost on either the suction hose or the pipe. This issue may also be caused by a faulty expansion valve, which should be replaced if the temperature sensor does not resolve the issue.
Low-Pressure Side Pressure is Too Low:
- Insufficient Refrigerant: If there is little temperature difference between the low-pressure and high-pressure sides, your device may be lacking in refrigerant. Ensure that there are no leaks in the unit, repair them if any are found, and then recharge the refrigerant to the correct level.
- Clogged Drier Tank: The most obvious sign of a clogged drier tank is visible frost on the tank. Alternatively, if there is a considerable temperature difference between the inlet and outlet sides, you may also have a clog. In either case, the liquid tank should be replaced to resolve the issue.
- Clogged Expansion Valve: Look for signs of frost on the expansion valve’s inlet side. If you notice these, you may need to replace the valve.
- Expansion Valve Temperature Sensor Gas Leak: Look for an unusually low, possibly negative, reading on the pressure gauge side, as well as signs of frost at the point of restriction and any chilling on the expansion valve’s outlet side. If you notice these issues, try cleaning the piping. If this does not work, replacing the piping should resolve the issue.
- Clogged or Blocked Piping: Begin by inspecting the point of restriction for signs of frost. Additionally, look for a low pressure gauge reading that is either abnormally low or negative. In this case, the piping should be cleaned to start, or replaced if cleaning is not sufficient to resolve the issue.
- Defective Thermo-Switch: Inspect the evaporator to see if it has frozen. If it has, first check the settings of the thermo-switch and adjust any erroneous settings. If this does not resolve the freezing issue, you should replace the thermo-switch.
High-Pressure Side Pressure is Too High:
- Poor Condenser Cooling: Look for debris or clogs in the condenser fans. If the fans are dirty, they may not operate correctly, and should be cleaned thoroughly.
- Excessive Refrigerant: If you suspect that excessive refrigerant is causing issues with the gauge pressure, verify the refrigerant level with a gauge reading. Capture any excess refrigerant with your refrigerant recovery equipment before charging back to the correct level.
- Air in the System: If the pressure is abnormally high on both the high and low sides, excess oxygen may have infiltrated the system. Evacuate the system and then recharge it with refrigerant to resume normal operations.
High-Pressure Side Pressure is Too Low:
- Insufficient Refrigerant: If the temperatures on the low-pressure and high-pressure sides are similar, you may be low on refrigerant. Search for and repair any leaks before charging the refrigerant back to the correct level.
Both the Low-Pressure Side and the High-Pressure Side Pressures are Too High:
- Improper Refrigerant Charge: This issue can be caused by the refrigerant being improperly charged. Check for either insufficient or excessive refrigerant charge, either repairing leaks or retrieving excess refrigerant as needed, before charging back to the correct levels.
- Improper Temperature Sensor Installation: Ensure that the temperature sensor is installed correctly and check the insulation for any issues. If you find any errors in these aspects, adjust to default specifications.
- Defective Expansion Valve: If you have tried both of the above, and the problem does not resolve, it is likely that you are having an issue with a defective expansion valve. At this point, you should replace the valve.
Insufficient Compressor Operations (High-Pressure Side Pressure is Too Low, and Low-Pressure Side Pressure is Too High, or the High-Pressure Side Pressure and Low-Pressure Side Pressure are Equal When Operation is Stopped):
- Damaged Suction Valve: Inspect the suction valve thoroughly for any signs of damage. If any damage is found, replace the valve.
- Defective Compressor Gasket: If the suction valve does not have any signs of damage, then the issue may lie with the compressor gasket, which should be replaced at this stage.
Need Additional Assistance?
Osage Ambulance is here for you! We have a variety of contact options to help you get in touch with our helpful staff. Alternatively, you can check out our other blog posts for more helpful fixes to common HVAC issues.
